I think their ideas have come from watching too many movies. Mystery Men comes to mind.
If really want to help, it takes some real training, not just the will or desire and some gadgets. Also, there's many issues that would be involved, like what if the so called superhero happens upon a man being beaten by another. who should he help? most would say defend the one being beaten... but what if the one being beaten was the robber who met a martial artist who beat him for trying to rob... etc. even police officers who go to a scuffle don't know who is the "good guy" or the "bad guy"
I don't think those self designated superheros have training or very little training, let alone would be able to do the right thing all the time. If really want to do good, should learn how to take care of family, protect friends and family only if need be... the search for criminals to "bring them to justice", that's the policeman's job.